1. Field of the Invention
The present invention relates to an automatic transmission.
2. Discussion of the Background
There is a known automatic transmission capable of changing gears using a planetary gear mechanism in outputting power of an internal-combustion engine through an output member (see, for example, Japanese Unexamined Patent Application Publication (KOKAI) No. 2007-205466, in particular, FIG. 1).
For the automatic transmission described in Japanese Unexamined Patent Application Publication (KOKAI) No. 2007-205466, the output member is connected to driving wheels through a final driven gear, and the final driven gear is configured to receive a driving force from a motor through a speed reducer. With the aim of preventing excessive rotation of the motor when a vehicle runs at high speed, for example, an engagement mechanism made of a synchromesh mechanism capable of breaking connection between the motor and the final driven gear is interposed between the motor and the final driven gear.
For the above-described example, the engagement mechanism dedicated to the motor provided to prevent excessive rotation of the motor breaks connection between the motor and the final driven gear if the output member is rotated at high speed. Therefore, it is necessary to have a space for use in the engagement mechanism dedicated to the motor, and this limits size and weight reduction.